第二讲--------缩略图放大

            在很多应用中，比如微信的朋友圈，QQ的空间，每条动态都会有很多图片，这些图片都是一些缩略图，点击后得到原图。如果细心的同学可能会注意到QQ空间里点击图片时，只有一个黑色背景和一个下载百分比进度背景，而微信下载大图时会把缩略图作为背景放在后面。

         这一讲就完成将缩略图作为背景，然后下载原图。

        整个过程分为3三步

        1、显示下载完成之前的提示正在下载页面

        2、线程从后台下载图片并存储

        3、下载完成后，将提示界面换成大图界面

        先上程序截图吧，进去的主界面，很简单，只有两个按钮，按测试按钮直接进入测试，因为对下载的大图进行了缓存，所以要重新测试的时候需要先清除原来缓存好的图片

     

按测试之后，进入下载提醒界面

       

下载完成后，大图可以放大、缩小、放大后可以左右移动

              

        首先下载是个耗时的过程，上一讲刚讲过后台耗时操作的处理，不过这里要用那个类的升级版。因为上一讲讲的那个下载过程中是不带UI的，所以稍微做了一下修改，主要代码如下，我每篇文章都会带小程序的，xml文件就不放上来了。

 

      

public abstract class ProgressDialogHandle {    private Context mContext;    private Dialog mDialog;    private static final String THREAD_NAME = "dataprocess_thread";    private static final int UPDATE = 1;    protected static final int DISMISS = 2;    protected static final int INVALIDEUSER = 3;    private HttpURLConnection conn;    private Bitmap backgound;    public ProgressDialogHandle(Context context) {        this.mContext = context;    }    public ProgressDialogHandle(Context context, HttpURLConnection conn) {        this.mContext = context;        this.conn = conn;    }    Handler messageHandler = new Handler() {        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what) {            case UPDATE:                break;            case DISMISS:                try {                    /* 执行这里的时候，判断对话框是否已经存在，不然直接执行dismiss可能会出现异常 */                    if (mDialog != null && mDialog.isShowing()) {                        mDialog.dismiss();                    }                } catch (Exception e) {                } finally {                    updateUI();                }                break;            default:                break;            }        }    };    public void show() {        if(mDialog == null){            mDialog = getProgressDialog(mContext, backgound);            mDialog.setOnCancelListener(new OnCancelListener() {                @Override                public void onCancel(DialogInterface dialog) {                    try {                        if (conn != null) {                            conn.disconnect();                            conn = null;                        }                    } catch (Exception e) {                        e.printStackTrace();                    }                }            });        }        mDialog.show();        new Thread(THREAD_NAME) {            public void run() {                try {                    handleData();                }                catch (Exception e) {                    e.printStackTrace();                } finally {                    Message.obtain(messageHandler, DISMISS).sendToTarget();                }            };        }.start();    }    public void dismiss() {        if (mDialog != null && mDialog.isShowing()) {            mDialog.dismiss();        }    }    public void setBackground(Bitmap backgound) {        this.backgound = backgound;    }    @SuppressLint("NewApi")        public static Dialog getProgressDialog(Context context, Bitmap bm) {        final Dialog dialog = new Dialog(context, R.style.progress_dialog);        dialog.setContentView(R.layout.progress_dialog_view);        if (bm != null) {            ImageView iv = (ImageView) dialog.findViewById(R.id.progress_iv);            iv.setImageBitmap(bm);        }        dialog.setCanceledOnTouchOutside(false);        return dialog;    }    public abstract void handleData() throws JSONException, IOException,            Exception;    public abstract String initialContent();    public abstract void updateUI();}

在使用的时候注意：要把缩略图做背景图显示的话，在调用show方法开始执行下载任务之前要先调用setBackgroud方法设置背景图片

大图浏览主类

package com.yixuan;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import org.json.JSONException;import com.example.handlertest.R;import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Matrix;import android.graphics.drawable.BitmapDrawable;import android.os.Bundle;import android.text.TextUtils;import android.util.DisplayMetrics;import android.view.GestureDetector;import android.view.MotionEvent;import android.widget.ImageView;import android.widget.Toast;/** * 大图预览 * 功能描述：一般我们浏览一个应用，别人发布的状态或新闻都会有很多配图， *          我们点击图片时可以浏览大图，这张大图一般可以放大，放大到超过屏幕后 *          可以移动 *需要从activity的Intent传参数过来 * 传入参数：url  大图下载地址 *          smallPath 缩略图存在本地的地址 * @author Administrator * */public class PicturePreviewActivity extends Activity{private ImageView zoomView;private Context ctx;private GestureDetector gestureDetector;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_picture_preview);ctx = this;zoomView = (ImageView) findViewById(R.id.zoom_view);/*大图的下载地址*/final String url = getIntent().getStringExtra("url");/*缩略图存储在本地的地址*/final String smallPath = getIntent().getStringExtra("smallPath");DisplayMetrics metrics = new DisplayMetrics();getWindowManager().getDefaultDisplay().getMetrics(metrics);final int widthPixels = metrics.widthPixels;final int heightPixels = metrics.heightPixels;if (!TextUtils.isEmpty(url)) {ProgressDialogHandle handle = new ProgressDialogHandle(this) {Bitmap bitmap = null;@Overridepublic void handleData() throws JSONException, IOException,Exception {bitmap = getBitMapFromUrl(url);}@Overridepublic String initialContent() {return null;}@Overridepublic void updateUI() {if (bitmap != null) {recycle();zoomView.setImageBitmap(zoomBitmap(bitmap, widthPixels,heightPixels));} else {Toast.makeText(ctx, R.string.download_failed,Toast.LENGTH_LONG).show();}}};handle.setBackground(BitmapFactory.decodeFile(smallPath));handle.show();}gestureDetector = new GestureDetector(this,new GestureDetector.SimpleOnGestureListener() {@Overridepublic boolean onFling(MotionEvent e1, MotionEvent e2,float velocityX, float velocityY) {float x = e2.getX() - e1.getX();if (x > 0) {prePicture();} else if (x < 0) {nextPicture();}return true;}});}protected void nextPicture() {// TODO Auto-generated method stub}protected void prePicture() {// TODO Auto-generated method stub}@Overridepublic void onResume() {super.onResume();recycle();}public void recycle() {if (zoomView != null && zoomView.getDrawable() != null) {BitmapDrawable bitmapDrawable = (BitmapDrawable) zoomView.getDrawable();if (bitmapDrawable != null && bitmapDrawable.getBitmap() != null&& !bitmapDrawable.getBitmap().isRecycled()){bitmapDrawable.getBitmap().recycle();}}}public Bitmap getBitMapFromUrl(String url) {Bitmap bitmap = null;URL u = null;HttpURLConnection conn = null;InputStream is = null;try {u = new URL(url);conn = (HttpURLConnection) u.openConnection();is = conn.getInputStream();bitmap = BitmapFactory.decodeStream(is);} catch (Exception e) {e.printStackTrace();} finally {try {if (is != null) {is.close();}} catch (IOException e) {e.printStackTrace();}conn.disconnect();}return bitmap;}@Overridepublic boolean onTouchEvent(MotionEvent event) {return gestureDetector.onTouchEvent(event);}/** * Resize the bitmap *  * @param bitmap * @param width * @param height * @return */public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {if (bitmap == null)return bitmap;int w = bitmap.getWidth();int h = bitmap.getHeight();Matrix matrix = new Matrix();float scaleWidth = ((float) width / w);float scaleHeight = ((float) height / h);if (scaleWidth < scaleHeight) {matrix.postScale(scaleWidth, scaleWidth);} else {matrix.postScale(scaleHeight, scaleHeight);}Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);return newbmp;}}

主类

package com.yixuan;import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import org.json.JSONException;import com.example.handlertest.R;import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Matrix;import android.graphics.drawable.BitmapDrawable;import android.os.Bundle;import android.os.Environment;import android.text.TextUtils;import android.util.DisplayMetrics;import android.view.GestureDetector;import android.view.MotionEvent;import android.widget.ImageView;import android.widget.Toast;/** * 大图预览 功能描述：一般我们浏览一个应用，别人发布的状态或新闻都会有很多配图， 我们点击图片时可以浏览大图，这张大图一般可以放大，放大到超过屏幕后 * 可以移动 需要从activity的Intent传参数过来 传入参数：url 大图下载地址 smallPath 缩略图存在本地的地址 *  * @author Administrator *  */public class PicturePreviewActivity extends Activity {private ImageView zoomView;private Context ctx;private GestureDetector gestureDetector;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_picture_preview);ctx = this;zoomView = (ImageView) findViewById(R.id.zoom_view);/* 大图的下载地址 */final String url = getIntent().getStringExtra("url");/* 缩略图存储在本地的地址 */final String smallPath = getIntent().getStringExtra("smallPath");DisplayMetrics metrics = new DisplayMetrics();getWindowManager().getDefaultDisplay().getMetrics(metrics);final int widthPixels = metrics.widthPixels;final int heightPixels = metrics.heightPixels;File bigPicFile = new File(getLocalPath(url));if (bigPicFile.exists()) {/* 如果已经下载过了,直接从本地文件中读取 */zoomView.setImageBitmap(zoomBitmap(BitmapFactory.decodeFile(getLocalPath(url)), widthPixels,heightPixels));} else if (!TextUtils.isEmpty(url)) {ProgressDialogHandle handle = new ProgressDialogHandle(this) {Bitmap bitmap = null;@Overridepublic void handleData() throws JSONException, IOException,Exception {bitmap = getBitMapFromUrl(url);}@Overridepublic String initialContent() {return null;}@Overridepublic void updateUI() {if (bitmap != null) {recycle();savePhotoToSDCard(bitmap, getLocalPath(url));zoomView.setImageBitmap(zoomBitmap(bitmap, widthPixels,heightPixels));} else {Toast.makeText(ctx, R.string.download_failed,Toast.LENGTH_LONG).show();}}};handle.setBackground(BitmapFactory.decodeFile(smallPath));handle.show();}gestureDetector = new GestureDetector(this,new GestureDetector.SimpleOnGestureListener() {@Overridepublic boolean onFling(MotionEvent e1, MotionEvent e2,float velocityX, float velocityY) {float x = e2.getX() - e1.getX();if (x > 0) {prePicture();} else if (x < 0) {nextPicture();}return true;}});}protected void nextPicture() {// TODO Auto-generated method stub}protected void prePicture() {// TODO Auto-generated method stub}@Overridepublic void onResume() {super.onResume();recycle();}public void recycle() {if (zoomView != null && zoomView.getDrawable() != null) {BitmapDrawable bitmapDrawable = (BitmapDrawable) zoomView.getDrawable();if (bitmapDrawable != null && bitmapDrawable.getBitmap() != null&& !bitmapDrawable.getBitmap().isRecycled()){bitmapDrawable.getBitmap().recycle();}}}public Bitmap getBitMapFromUrl(String url) {Bitmap bitmap = null;URL u = null;HttpURLConnection conn = null;InputStream is = null;try {u = new URL(url);conn = (HttpURLConnection) u.openConnection();is = conn.getInputStream();bitmap = BitmapFactory.decodeStream(is);} catch (Exception e) {e.printStackTrace();} finally {try {if (is != null) {is.close();}} catch (IOException e) {e.printStackTrace();}conn.disconnect();}return bitmap;}@Overridepublic boolean onTouchEvent(MotionEvent event) {return gestureDetector.onTouchEvent(event);}/** * Resize the bitmap *  * @param bitmap * @param width * @param height * @return */public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {if (bitmap == null)return bitmap;int w = bitmap.getWidth();int h = bitmap.getHeight();Matrix matrix = new Matrix();float scaleWidth = ((float) width / w);float scaleHeight = ((float) height / h);if (scaleWidth < scaleHeight) {matrix.postScale(scaleWidth, scaleWidth);} else {matrix.postScale(scaleHeight, scaleHeight);}Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);return newbmp;}public static String getLocalPath(String url) {String fileName = "temp.png";if (url != null) {if (url.contains("/")) {fileName = url.substring(url.lastIndexOf("/") + 1, url.length());}fileName = fileName.replaceAll("&", "").replaceAll("%", "").replaceAll("?", "");}return Environment.getExternalStorageDirectory() + fileName;}/** * Save image to the SD card *  * @param photoBitmap * @param photoName * @param path */public static void savePhotoToSDCard(Bitmap photoBitmap, String fullPath) {if (checkSDCardAvailable()) {File file = new File(fullPath);if (!file.getParentFile().exists()) {file.getParentFile().mkdirs();}File photoFile = new File(fullPath);FileOutputStream fileOutputStream = null;try {fileOutputStream = new FileOutputStream(photoFile);if (photoBitmap != null) {if (photoBitmap.compress(Bitmap.CompressFormat.PNG, 100,fileOutputStream)) {fileOutputStream.flush();}}} catch (FileNotFoundException e) {photoFile.delete();e.printStackTrace();} catch (IOException e) {photoFile.delete();e.printStackTrace();} finally {try {fileOutputStream.close();photoBitmap.recycle();} catch (IOException e) {e.printStackTrace();}}}}public static boolean checkSDCardAvailable() {return android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED);}}

示例程序下载地址：http://download.csdn.net/download/u010047390/8466837